The invention relates to a high-pressure cleaning appliance with a high-pressure pump, comprising at least one pump chamber which is connected to a suction line and a pressure line, the pressure line being in flow connection with the suction line via a return flow line, and a relief valve being arranged in the return flow line, the relief valve having a through-channel, which extends from a valve inlet to a first valve outlet, and which forms a valve seat, at least one outlet channel, which opens into a second valve outlet, branching off from the through-channel downstream of the valve seat, and a valve element adapted to be positioned by a return spring in a sealing manner against the valve seat being held for movement in the through-channel.
Such high-pressure cleaning appliances are known from DE 297 12 659 U1. A surface to be cleaned can be acted upon with a pressurized cleaning liquid, for example, with water, by means of these. For this purpose, a high-pressure hose carrying at its free end, for example, a spray lance for spraying the surface to be cleaned can be connected to the pressure line.
During normal operation, cleaning liquid can be supplied to the pump chamber via the suction line. The cleaning liquid is pressurized inside the pump chamber, for example, by means of a piston which is reciprocatingly displaceable and enters the pump chamber. The pressurized cleaning liquid can then be fed to a consumer via the pressure line. In this operating state, the relief valve is in its closed position, so that the direct connection between the pressure line and the suction line via the return flow line is interrupted. When a certain pressure value inside the pressure line is exceeded, as occurs, for example, upon closing a spray lance connected to the free end of the high-pressure hose, the relief valve transfers to its open position by the valve element, in opposition to the returning force exerted by the return spring, lifting off of the valve seat, so that cleaning liquid can flow back directly from the pressure line via the return flow line through the relief valve to the suction line and the pressure in the pressure line thereby dropping. The pressure drop may have the consequence that shortly after lifting off of the valve seat, the valve element is pressed back onto the valve seat again by the return spring, to then lift off of the valve seat again. The transition of the relief valve from the closed position to the open position of the relief valve may therefore be accompanied by an oscillating movement of the valve element and the return spring. This oscillating movement constitutes a considerable mechanical load. This may lead to failure of the high-pressure cleaning appliance.